If it's like this after just a few months then imagine what it might be like in a few more months...
...something is going to have to give as things obviously can't continue as you're describing them.
In the short term, you may want to look at a way of reducing the number of emails coming in. Options could include:
1) Stress on the site UK enquiries only and politely explain that with the best will in the world you simply don't have the time to answer non-UK emails.
2) [optional] Stick an auto-responder on your email system that explains your position, for example, "Thank you for your enquiry, we're pretty busy right now but aim to reply to UK drivers within 72 hours. Unfortunately, as explained on our web site, we're currently unable to answer queries from outside the UK." This means you can then immediately delete any non-UK stuff without any guilty conscience.
3) Maybe stick a "Geometry Forum" on your site where users can post alignment questions and only you can post replies? I'm guessing that the same old problems will crop up and by posting a specific solution to a particular type of problem, the next 20 people with the same problem can read your answer immediately without sending you 20 emails? So after a short while, a lot of the more common queries would be answered and you'd hopefully be left with just the new interesting problems and a lot less of them!
4) Instead of having your email address on the site for all and sundry to email you, use a form system instead. This would be a series of questions and answers that the user goes through by clicking links, hopefully many would find the answer they're looking for and those that don't can then submit their questions to you.
In the long term... well I think you know you need to make some tough decisions.